Diaz-Montero et al. [26] and Solito et al. [27] identified MDSC as Lin−/lowHLA-DR−CD33+CD11b+ cells in patients with advanced breast cancers, while Yu et al. identified MDSC as CD45+CD13+CD14−CD15− cells with suppressive activity, assessed through IDO expression and reported expansion that correlated with lymph node metastasis in breast cancer patients [28]. Here, IDO1 is linked to breast cancer.